The present invention relates to the manufacture of tires. More precisely, it relates to the depositing of cords to constitute a tire reinforcement. More particularly, it proposes means suitable for manufacturing such a reinforcement on a form similar or identical to the form of the internal cavity of the tire, that is to say a substantially toroidal form.
In this technical field, processes and apparatus are already known which permit incorporation of the manufacture of the tire reinforcements into assembly of the tire itself. This means that, rather than having recourse to semi-finished products, such as reinforcement plies, one or more reinforcements are produced in situ, at the time of manufacture of the tire, from a cord spool. Of these processes and apparatus, the solution described in U.S. Pat. No. 5,453,140 is most particularly adapted for producing carcass reinforcements on a rigid core, the outer surface of which corresponds substantially to the form of the internal cavity of the finished tire. This patent discloses equipment in which the cord, intended to constitute a carcass reinforcement, is laid down in contiguous arches on a rigid core, via an eyelet fixed on a chain mounted on pulleys in such a way as to surround the core by forming a type of fork. The eyelet performs a to-and-fro movement around the core in such a way as progressively and contiguously to deposit an arch with each outward movement and an arch with each return movement, suitable pressers being used to apply the ends of said arches as they are formed on the rigid core pre-coated with uncured rubber.
The object of the present invention is to propose an improvement allowing laying down of a reinforcing cord on a core with more possibilities for controlling the final trajectory on the core.
The invention proposes an apparatus for manufacturing a tire reinforcement, said apparatus being intended for manufacturing a reinforcement constituted from a cord supplied continuously and on demand by a suitable distributor, said apparatus being intended for use in cooperation with a substantially toroidal form on which said reinforcement is built up progressively by laying arches of said cord, according to a final trajectory desired for said cord, down on the surface of said form, said apparatus comprising depositing members arranged on a support, the depositing members comprising:
a guide member in which the cord may slide freely,
a mechanism for actuating said guide member in a cyclical, to-and-fro, movement, to bring said guide member in successive oscillations into the vicinity of each of the ends desired for the cord in said trajectory, said apparatus comprising pressers close to each end of said trajectory, for applying the cord onto the form at said ends, characterized in that the apparatus comprises means of imparting to the depositing member support an alternating movement synchronized with the movement of the actuating mechanism, allowing deflection of the final cord trajectory on the form.
Reference should be made to the aforesaid patent, since the present invention includes not only the process described therein but also to a considerable extent the pressers used to allow formation of a loop and to apply said loop against the core. By way of a reminder, the pressers essentially each comprise a fork and a hammer. Apart from a few details, the presser embodiment described therein could be used as it is, even if a novel form is proposed below for said pressers.
Before embarking on a detailed description of these novel means of actuating the cord guide member, it would be helpful to remember certain useful points.
First of all, it should be noted that, as in the above-cited patent, the term xe2x80x9ccordxe2x80x9d must be understood in a completely general sense, covering a monofilament, a multifilament, an assembly such as for example a cable or a plied yarn, or a small number of grouped cables or plied yarns, whatever the nature of the material and whether or not the xe2x80x9ccordxe2x80x9d is pre-coated with rubber. In the present specification, the term xe2x80x9carchxe2x80x9d is used to designate a portion of cord extending from a singular point to another in the reinforcement armature. All these arches disposed over the entire periphery of the tire form the reinforcement proper. An arch as defined here may be part of a carcass or of a crown reinforcement or of any other type of reinforcement. These arches may be separated by cutting the cord during depositing thereof, or they may all be connected together in the finished reinforcement, for example by loops.
Basically, the invention relates to continuous deposition of a reinforcing cord, in a configuration as close as possible to the configuration in the finished product. Since the cord is supplied on demand by a suitable distributor comprising for example a cord spool and, if applicable, a device for controlling the tension of the cord withdrawn from the spool, the apparatus for manufacturing a reinforcement from a cord cooperates with a form (rigid core or reinforced membrane) on which the tire is manufactured. It is of little significance whether the reinforcement, to be complete, is fabricated in several successive passes of the depositing members described with or without cutting of the cord between two passes.
When positions or directions are defined by the words xe2x80x9cradially, axially, circumferentiallyxe2x80x9d or when radii are mentioned, the reference point is taken to be the core on which the tire is manufactured, or the tire itself, which comes to the same thing. The geometric axis of reference is the axis of rotation of the form.
Likewise, as has already been pointed out in the above-cited patent, the cord depositing members described here also allow the production of a reinforcement, for example a carcass reinforcement, in which the laying pitch of the cord is variable. xe2x80x9cLaying pitchxe2x80x9d is understood to mean the distance resulting from the sum of the space between two adjacent cords and the diameter of the cord. It is well known that, for a carcass reinforcement, the space between cords varies according to the radius at which it is measured. This is not the variation referred to here, which is a variable pitch at a given radius. For this, it is sufficient to vary the speed of rotation of the form as a function of any suitable law without changing the working speed of the guide member. A tire is thus obtained, the carcass reinforcing cords of which, for example for a radial carcass, are disposed at a pitch exhibiting controlled variation for a given radial position.
Various embodiments of the cord depositing members may be envisaged. There are described below various embodiments of said depositing members which constitute the subject matter of the application FR00/01393 filed on Feb. 1, 2000 and corresponding to U.S. Ser. No. 09/773,985 filed Feb. 1, 2001. The first embodiment uses a series of three functional oscillating arms. In addition, possible variants are described for this first embodiment. A series of three functional oscillating arms is preferably used for depositing carcass arches extending from one bead to the other of the tire. The second embodiment uses a series of two functional oscillating arms. Furthermore, a variant embodiment is given for this second embodiment. A series of two functional oscillating arms is used for example for depositing carcass arches extending from a bead to a shoulder of the tire. The third embodiment uses a single functional oscillating arm, which is sufficient for the simplest deposition to be performed.
When xe2x80x9cnxe2x80x9d functional oscillating arms are used which are arranged in series (n greater than 1), the term xe2x80x9cnth armxe2x80x9d is used to designate the functional oscillating arm to which the cord guide member is directly fixed, the base arm always being the xe2x80x9cfirst oscillating armxe2x80x9d. The oscillating arms are arranged in series in such a way that, in general, the conveying head of the oscillating arm xe2x80x9cpxe2x80x9d (p being less than n) conveys the center of rotation of the oscillating arm xe2x80x9cp+1xe2x80x9d. This is why it is stated above that the conveying head conveys the cord guide member directly, or only xe2x80x9cindirectlyxe2x80x9d (that is to say through the intermediary of one or more other functional oscillating arms). In all the examples described, the geometric axis of the center of rotation of the first oscillating arm is, in the working position, entirely exterior to the form, with which it never comes into contact, that is to say not even via its extensions.
The apparatus causes the cord guide member to describe a movement which is substantially included in a planexe2x80x94the plane of movementxe2x80x94perpendicular to the geometric axis of rotation of the base arm. In another aspect of the apparatus according to the invention, the base arm, or according to the variants, each of the oscillating arms used, is of planar, long-limbed appearance, and the base arm oscillates in this plane of movement, or all the oscillating arms move in parallel, neighboring planes, one of them being very close to this plane of movement, or even merged with this plane of movement, depending on the type of guide member used.
Emphasis should also be laid on the fact that, according to one aspect of the reinforcing cord arch depositing principle here under consideration, an actuating mechanism causes the cord guide member to describe a movement substantially included in a planexe2x80x94the plane of movement. When the invention is applied to an actuating mechanism of said guide member comprising a chain as described in U.S. Pat. No. 5,453,140, the plane of movement is the plane described by the eyelet xe2x80x9833xe2x80x99 (a reference numeral thus identified constituting a reference to the drawings of U.S. Pat. No. 5,453,140. This plane is perpendicular to the axis of rotation of the pulleys guiding the chain 30. It may be considered that the depositing member support is the framework 51 of the presentation device 5. When applied to the machine described in the above-cited patent application, the invention consists, for example, in actuating said framework 51 with an alternating translational movement perpendicular to the plane of movement, in synchronism with the movement of the eyelet 33 in said plane of movement, to act on the deposition trajectory of the cord 4 on the form 1. The framework 51 may be actuated, for example, by interposing a suitable mechanism between the slide rail 50 and the frame 2 or between the framework 51 and the slide rail 50. In this way, the trajectory according to which the cord is deposited on the surface of the core also depends on this movement perpendicular to the plane of movement. Thus, if said framework 51 is displaced as indicated (translational movement perpendicular to the plane of movement) over a predetermined distance while the eyelet 33 passes from the zone close to one bead to the zone close to the other bead, the cord arch deposited is not arranged radially, but rather forms an angle which is not zero, as in the case shown in FIG. 12 below.
The description which follows affords a full understanding of a particular instance of the invention when applied to the members which constitute the subject matter of application FR00/01393.